Elevated CO2 and temperature under future climate change increase severity of rice sheath blight

Abstract

Sheath blight (ShB), caused by <i>Rhizoctonia solani</i>, is one of the major threats to rice (<i>Oryza sativa</i> L.) production. However, it is not clear how the risk of rice ShB will respond to elevated CO₂ and temperature under future climate change. Here, we conducted, field experiments of inoculated <i>R. solani</i> under combinations of two CO₂ levels (ambient and enriched up to 590 μmol mol^-1) and two temperature levels (ambient and increased by 2.0°C) in temperature by free-air CO₂ enrichment (T-FACE) system for two cultivars (a susceptible cultivar, Lemont and a resistant cultivar, YSBR1). Results indicate that for the inoculation of plants with <i>R. solani</i>, the vertical length of ShB lesions for cv. Lemont was significantly longer than that for cv. YSBR1 under four CO₂ and temperature treatments. The vertical length of ShB lesions was significantly increased by elevated temperature, but not by elevated CO₂, for both cultivars. The vertical length of ShB lesions under the combination of elevated CO₂ and elevated temperature was increased by 21-38% for cv. Lemont and by -1-6% for cv. YSBR1. A significant increase in MDA level was related to a significant increase in the vertical length of ShB lesions under the combination of elevated CO₂ and elevated temperature. Elevated CO₂ could not compensate for the negative effect of elevated temperature on yield of both cultivars under future climate change. Rice yield and biomass were further decreased by 2.0-2.5% and 2.9-4.2% by an increase in the severity of ShB under the combination of elevated CO₂ and elevated temperature. Thus, reasonable agronomic management practices are required to improve both resistance to ShB disease and grain yield for rice under future climate change.